1. Field of the Invention
The present invention relates to a grinding machine for grinding with continuous dressing for a workpiece with a rotating grinding wheel and for normally grinding except for the grinding with continuous dressing.
2. Description of the Related Art
The grinding with continuous dressing, in which a dressing device is provided onto a grinding machine or a grinding center and an operation for dressing a grinding wheel with the dressing device and an operation of grinding the workpiece with the grinding wheel are performed simultaneously, is well known in the art, for example, MACHINE TOOL SERIES, ADVANCED GRINDING TECHNOLOGY (published by Kabushiki Kaisha Taigashuppan on Sep. 20, 1985, pages 55-60) entitled "CONTINUOUS DRESSING-CREEP FEED GRINDING" or the like.
Also, Examined Japanese Patent Publication No. Hei. 3-27342 discloses a grinding machine provided with a dressing device with two grinding spindles.
However, the grinding machine which is disclosed in the above-described Japanese Patent Publication No. Hei 3-27342 takes a structure such that a grinding spindle carrier is moved up and down relative to a column and the dressing device is moved up and down relative to the grinding spindle carrier.
For this reason, it is impossible to move only a grinding head carried on the grinding spindle supported to the grinding spindle carrier. Namely, it is impossible to move only a grinding wheel of the grinding head.
Accordingly, it is difficult to grind a workpiece while a dressing tool and the grinding wheel are separated far away from each other and the grinding wheel is moved round the workpiece so as to avoid an interference between the workpiece and the dressing tool of the dressing device.
Also, the grinding spindle carrier, the column, a motor and a spindle drive portion, or the like, become large in size when the amount of movement of a frame of the dressing device relative to the grinding spindle carrier is increased in order to keep the dressing tool far away from the grinding wheel. In this case, it is necessary to increase an energy consumption since the respective enlarged components should be moved. As a result, the cost is increased.
Furthermore, the grinding machine is provided with two grinding spindle carriers for supporting the grinding spindles and the grinding head having a plurality of grinding wheels is supported to each grinding spindle and a s ingle workpiece may be simultaneously ground by the grinding heads from opposite sides so that the grinding machine is complicatedly structured.
This structure would be suitable for the grinding for specific kinds of turbine blades but suffers from a problem in versatility in order to grind various kinds of workpieces.
Also, Japanese Patent Application Laid-Open No. Sho 62-199359 and Examined Japanese Patent Publication No. Hei 6-37031 disclose a technology for grinding with continuous dressing with a grinding machine. However, according to these pieces of the prior art, a dresser and a dresser driving portion, or the like, are provided on a grinding wheel head, accordingly, it is impossible to keep the dresser, or the like, far away from a grinding wheel and to perform the grinding while the grinding wheel is moved round a workpiece.